Congenital anomalies are the second leading cause of perinatal mortality in the United States after premature birth. Advances in imaging techniques have allowed the detection of many anatomical defects with ultrasound before birth. The goal of this project is to improve the diagnosis and treatment of fetal disease and congenital anomalies. The Perinatology Research Branch has initiated a series of projects to improve the detection of congenital anomalies and assess fetal growth and development with the use of three-dimensional ultrasound. The findings of this year include the following: 1. A systematic approach to the examination of the fetal mandible was developed with the goal of improving the diagnosis of micrognathia. This condition is present in over 211 genetic syndromes and is difficult to diagnose prenatally. Orthogonal multiplanar views obtained with three-dimensional ultrasound were used to assess the midsagittal facial profile. This approach was used to evaluate fetuses at risk. Three-dimensional ultrasound improves visualization of the fetal profile and, hence, the diagnosis of micrognathia. Diagnostic pitfalls were identified. 2. Three-dimensional ultrasound was used to examine the fetal spine in the evaluation of fetuses suspected to have spina bifida and to characterize the extent of the defect. Two- and three-dimensional ultrasound was used to determine the extent of vertebral defects among affected fetuses, and this information was compared with postnatal analyses of spinal defects derived from radiographic films of magnetic resonance imaging. Three-dimensional sonography findings agreed within one vertebral segment in 8 of 9 affected infants. Volume rendering showed splayed vertebral pedicles and disrupted vertebrae. An intact meningeal sac was easily rendered in 5 of 9 subjects. Multiplanar views were more informative than rendered views for localizing bony defects of the fetal spine. These observations have clinical relevance because spina bifida is the most common and difficult to diagnosis neural tube defect. Moreover, the degree of disability of affected individuals (paraplegia, sensory deficits, spinal deformity, bowel dysfunction, and urinary incontinence) is a function of the location and extent of the spinal defect. Three-dimensional ultrasound offers a means to improve the characterization of the scope of the spinal defect. 3. A cost-effectiveness study determined that a policy of offering genetic sonography followed by amniocentesis to patients 35 years and older who originally decline invasive testing for the diagnosis of trisomy 21 is cost-effective and results in a higher overall detection rate without an increased risk of pregnancy loss. 4. Three-dimensional ultrasound was used to assess the presence or absence of the nasal bone in fetuses with and without trisomy 21. The impetus for this study was a recent report suggesting that the absence of a nasal bone may identify fetuses with trisomy 21 in the first trimester of pregnancy. Yet, the value of this sign in the assessment of fetuses at risk in the second or third trimester is unknown. The Branch determined that the absence of a nasal bone had a 40% sensitivity and an 80% specificity in the detection of trisomy 21. Three-dimensional ultrasound allowed standardization of the diagnosis.